1. Field of the Invention
The present invention relates generally to an automatic automotive transmission and more specifically to a range selection control arrangement for such a transmission.
2. Description of the Prior Art
JP-A-62-62047 discloses a transmission which includes a power train comprising two planetary gear units which are operated by plurality of clutches and brakes. Depending on the engagement/disengagement of the various friction elements a plurality of forward speed can be selectively produced.
JP-A-61-244957 discloses an auxiliary gear unit which can be connected to the output shaft of a gear train of the type mentioned above for the purposes of increasing the number of forward speeds which can be produced.
The JP-A-62-62047 type transmission is capable of producing four forward speeds while the auxiliary gear unit can be produce two different gear ratios. Accordingly the combination of the main and auxiliary gear trains are capable of producing a total of 8 gear ratios. 5 of these gear ratios can be selected without encountering abnormal amounts of shift shock.
However, with this type of arrangement in the event that the select level is manipulated it is possible to limit the number of gear ratios between which shifting can occur.
In the case of the four speed transmission, the select lever can be moved between parking (P), reverse (R), neutral (N), drive (D), manual 2 (II) and manual 1 (I). The select lever is further provided with a overdirve (OD) inhibit switch which enables the transmission from being inhibited from shifting into fourth speed.
In the case of the provision of the auxiliary gear unit, fifth speed becomes the overdrive range and a manual 3 range (III) is added to the positions in which the select lever can be set.
In addition, in the case of the five speed transmission, the manual ranges in which engine braking can be induced are predetermined.
However, with this type of transmission the manual ranges are P, R, N, D, III, II and I. Viz., there are three forward ranges which can be selected. In order to induce engine braking the select level is permitted to be freely moved from D range to manual 2 range (II). In order to prevent excessive engine braking which can result in damage to the transmission or associated power train, the select lever is normally prevented from moving directly into manual first range (I).
Further, due to the increased number of selectable positions--viz., P, R, N, D, III, II & 1, the stroke of the select lever is increased to the degree that layout problems are induced. That is to say, the ergonomic dispositioning of the select lever with respect to the hand brake lever, the center arm rest and the consoles located between the hump on which the floor shift is mounted and the dashpanel, becomes difficult.